A charity has accused one of the world's biggest content delivery networks of inadvertently protecting sites that host images of child abuse.
Cloudflare helps websites deliver content faster but some of its clients are known to host illegal content.
The company insists it is powerless because it does not actually host the offending sites.
Campaigners say Cloudflare's services make it easier for clients to avoid detection by "hiding" their locations.
The anti-child-abuse campaign Battling Against Demeaning & Abusive Selfie Sharing claims to have first made the internet company aware of numerous indecent images, including some showing child sexual abuse, on three of its clients' websites over a year ago.
The websites in question reportedly state any takedown notice would be ignored.
And one allegedly allows users to search through a catalogue of abusive images.
Following a Twitter campaign, Cloudflare director of trust and safety Justin Paine asked the charity send a detailed report of its complaint.
"We hope that by making noise, we will finally receive a response from Cloudflare. We're hopeful that they will end their relationship with these sites that profit off the exploitation of non-consenting women and and girls," charity advocate Emily Wilson told the BBC.
"All of our efforts have made no difference, and we are now publicizing our efforts to get some public pressure."
Cloudflare states on its website offensive content can be reported through a form, the details of which may then be shared with law enforcement officials if the complaint is deemed legitimate.
BBC News has contacted Cloudflare for comment.
It is not the first time the company has had to defend itself against claims it makes the takedown of illegal content tougher.
The internet giant hit back at the Motion Picture Association earlier this month after the American film body included it in a piracy complaint lodged with the US government.
A Cloudflare representative said at the time: "Cloudflare does not host the referenced websites, cannot block websites, and is not in the business of hiding companies that host illegal content - all facts well known to the industry groups based on our ongoing work with them."
Earlier this year, Cloudflare released a statement confirming it had terminated its services to 8chan, an internet forum used to celebrate mass shootings and spread so-called "manifestos".
It had previously pulled its services from neo-Nazi website The Daily Stormer.
Losing Cloudflare's protection made 8chan vulnerable to a distributed denial of service (DDoS) attack, whereby a website is bombarded with traffic that overwhelms its servers, rendering it inaccessible.
A few minutes after the Cloudflare service was withdrawn, 8chan did indeed become unavailable.